selftests/bpf: Test rhtab kptr cancellation semanticsgrafted

Resizable hash-map updates and deletions must not perform full special-field
destruction in their caller context. In particular, a referenced kptr must
remain attached to the allocation until the memory allocator destructor can
release it safely.

Add separate coverage for both affected paths. The update test stores a task
kptr, replaces the ordinary value bytes with BPF_EXIST, and verifies that the
kptr survived. The delete test removes an element and exchanges its kptr
through the still-valid map-value pointer before the allocation is reclaimed.

Both cases observe a NULL kptr when rhtab uses bpf_obj_free_fields(). They
recover and release the reference after rhtab switches to cancellation
semantics.

Signed-off-by: Nuoqi Gui <gnq25@mails.tsinghua.edu.cn>
[ kkd: Split update and delete coverage and rewrote the commit log ]
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904104203.345917-5-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 87 insertions, 0 deletions

diff --git a/drivers/acpi/tiny-power-button.c b/drivers/acpi/tiny-power-button.c
new file mode 100644
index 000000000..92516ef84
--- /dev/null
+++ b/drivers/acpi/tiny-power-button.c
@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/sched/signal.h>
+#include <acpi/button.h>
+
+MODULE_AUTHOR("Josh Triplett");
+MODULE_DESCRIPTION("ACPI Tiny Power Button Driver");
+MODULE_LICENSE("GPL");
+
+static int power_signal __read_mostly = CONFIG_ACPI_TINY_POWER_BUTTON_SIGNAL;
+module_param(power_signal, int, 0644);
+MODULE_PARM_DESC(power_signal, "Power button sends this signal to init");
+
+static const struct acpi_device_id tiny_power_button_device_ids[] = {
+	{ ACPI_BUTTON_HID_POWER, 0 },
+	{ ACPI_BUTTON_HID_POWERF, 0 },
+	{ "", 0 },
+};
+MODULE_DEVICE_TABLE(acpi, tiny_power_button_device_ids);
+
+static void acpi_tiny_power_button_notify(acpi_handle handle, u32 event, void *data)
+{
+	kill_cad_pid(power_signal, 1);
+}
+
+static void acpi_tiny_power_button_notify_run(void *not_used)
+{
+	acpi_tiny_power_button_notify(NULL, ACPI_FIXED_HARDWARE_EVENT, NULL);
+}
+
+static u32 acpi_tiny_power_button_event(void *not_used)
+{
+	acpi_os_execute(OSL_NOTIFY_HANDLER, acpi_tiny_power_button_notify_run, NULL);
+	return ACPI_INTERRUPT_HANDLED;
+}
+
+static int acpi_tiny_power_button_probe(struct platform_device *pdev)
+{
+	struct acpi_device *device;
+	acpi_status status;
+
+	device = ACPI_COMPANION(&pdev->dev);
+	if (!device)
+		return -ENODEV;
+
+	if (device->device_type == ACPI_BUS_TYPE_POWER_BUTTON) {
+		status = acpi_install_fixed_event_handler(ACPI_EVENT_POWER_BUTTON,
+							  acpi_tiny_power_button_event,
+							  NULL);
+	} else {
+		status = acpi_install_notify_handler(device->handle,
+						     ACPI_DEVICE_NOTIFY,
+						     acpi_tiny_power_button_notify,
+						     NULL);
+	}
+	if (ACPI_FAILURE(status))
+		return -ENODEV;
+
+	return 0;
+}
+
+static void acpi_tiny_power_button_remove(struct platform_device *pdev)
+{
+	struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
+
+	if (device->device_type == ACPI_BUS_TYPE_POWER_BUTTON) {
+		acpi_remove_fixed_event_handler(ACPI_EVENT_POWER_BUTTON,
+						acpi_tiny_power_button_event);
+	} else {
+		acpi_remove_notify_handler(device->handle, ACPI_DEVICE_NOTIFY,
+					   acpi_tiny_power_button_notify);
+	}
+	acpi_os_wait_events_complete();
+}
+
+static struct platform_driver acpi_tiny_power_button_driver = {
+	.probe = acpi_tiny_power_button_probe,
+	.remove = acpi_tiny_power_button_remove,
+	.driver = {
+		.name = "acpi-tiny-power-button",
+		.acpi_match_table = tiny_power_button_device_ids,
+	},
+};
+
+module_platform_driver(acpi_tiny_power_button_driver);